A batter module has a case, which is one of core components of the battery module, and the interior of which forms a space for accommodating battery cells. The case of a conventional battery module mainly includes a pair of side plates, a pair of end plates, a bottom plate and a top plate. The side plates and end plates mainly employ the following two structural forms.
In a first form, the side and end plates both are made of aluminum plates and are welded together. By adopting this structure, the weld strength between the side plates and the end plates is relatively low, resulting in a poor structural reliability of the battery module.
In a second form, the side and end plates both are made of steel plates and are welded together. Since steel plates are relatively heavy, the thickness of side and end plates are typically thin with less rigidity, causing the case of the battery module easily to be deformed due to the battery's expansion force.